The present invention relates to a flowmeter for measuring the flow of a fluid through a pipeline. More particularly, the present invention relates to an insertion flowmeter that permits a fluid flow detector to be automatically inserted into the fluid flow within the pipeline or retracted from the pipeline.
Insertion flowmeters for detecting the fluid flow through a pipeline and converting the data to engineering units are finding use in a wide variety of applications which include mass flow measurement and pipeline leak detection. Insertion flowmeters basically consist of a turbine meter on a stem, which in inserted into the fluid flow within a pipeline. The turbine meter comprises a rotor assembly having a precision rotor that turns through a magnetic field of force. As the rotor turns, passage of the blades past a pick-up sensor cuts the lines of force of the magnetic field and generates electronic pulses. The pulse output is applied to an electronic unit that converts the raw pulses from the turbine meter into engineering units for direct reading in standard cubic feet, pounds, kilograms, etc. Typically, the electronic units are frequency to voltage converters with rate indicators or linear analog control outputs. The electronic units can also, however, be flow computers, flare stack controllers, or leak detection systems.
Insertion flowmeters are installed on a section of pipeline by welding a flanged riser to the side wall of a pipeline. A flanged valve body is bolted on the riser. The valve includes a threaded stem which carries the rotor on the lower end thereof. To insert the turbine meter rotor into the fluid flowing in the pipeline or retract the rotor from the pipeline and into the riser, the valve stem is advanced into or backed out of the valve body by manual rotation. It has been found that after extended periods of use, the threads on the valve stem have a tendency to become galled and difficulty is experienced in movement of the stem.
Another problem presented by prior art insertion flowmeters is that on lengthly pipelines through sparsely populated or unpopulated areas, many of the flowmeters will be located at unmanned locations. Therefore, if it is necessary to retract a turbine meter from within the pipeline as, for example, when it is necessary to run a pig through the pipeline to clean parafin buildup therefrom, service personnel must be sent out to each unmanned location to manually retract the turbine wheel.
Accordingly, it would be most advantageous to provide an insertion flowmeter that does not utilize a threaded valve stem for effecting insertion and retraction of the turbine meter rotor. Also, it would be desirable to provide insertion flowmeter apparatus that can be remotely controlled from a distance of several hundred or even thousands of miles away from the actual location of the flowmeter itself.